"The U.S. Secret Service in coordination with local law enforcement in Glendale, Arizona, is investigating an individual who was observed exhibiting suspicious behavior at State Farm Stadium," Secret Service spokesperson Anthony Guglielmi told Fox News Digital on Saturday.

"The individual was approached by Secret Service and stated during the encounter that he was a member of law enforcement and that he was armed. The individual is not a member of authorized law enforcement working the event and is currently in custody," Guglielmi added.

The individual, who has not been publicly identified, actually was armed, Guglielmi confirmed to Fox News Digital.

"The U.S. Secret Service and local law enforcement are investigating the circumstances as to why he was at the location," he also said.

President Donald Trump and Vice President JD Vance are among the speakers set to honor Kirk on Sunday at the event.